LVM

LVM(Logical Volume Manager，逻辑卷管理器)是Linux下对磁盘分区进行管理的一种机制。

基本术语：

　　PV(physical volume，物理卷)指硬盘分区或者从逻辑上看和硬盘分区类似的设备

　　VG(volume group，卷组)类似于非LVM系统的物理硬盘，一个LVM卷组由一个或多个物理卷组成

　　LV(logical volume，逻辑卷)类似于非LVM系统的硬盘分区，LV建立在VG上，可以在LV上建立文件系统

　　PE(physical extent)PV中可以分配的最小存储单元，PE的大小可以指定，默认为4MB

　　LE(logical extent)LV中可以分配的最小存储单元，在同一个卷组上，LE的大小和PE是一样的，且一一对应

　　

安装：　　

rpm -qa | grep lvm
yum install -y lvm2*

 LVM的创建与管理

1、创建物理分区，通过fdisk创建类型为LVM的分区

fdisk -l /dev/sdb /dev/sdc

Disk /dev/sdb: 21.5 GB, 21474836480 bytes, 41943040 sectors
Units = sectors of 1 * 512 = 512 bytes
Sector size (logical/physical): 512 bytes / 512 bytes
I/O size (minimum/optimal): 512 bytes / 512 bytes
Disk label type: dos
Disk identifier: 0x5aea1fae

   Device Boot      Start         End      Blocks   Id  System
/dev/sdb1            2048     4196351     2097152   8e  Linux LVM
/dev/sdb2         4196352    12584959     4194304   8e  Linux LVM
/dev/sdb3        12584960    41943039    14679040   8e  Linux LVM

Disk /dev/sdc: 10.7 GB, 10737418240 bytes, 20971520 sectors
Units = sectors of 1 * 512 = 512 bytes
Sector size (logical/physical): 512 bytes / 512 bytes
I/O size (minimum/optimal): 512 bytes / 512 bytes
Disk label type: dos
Disk identifier: 0xda670c21

   Device Boot      Start         End      Blocks   Id  System
/dev/sdc1            2048     4196351     2097152   83  Linux
/dev/sdc2         4196352    10487807     3145728   8e  Linux LVM
/dev/sdc3        10487808    18876415     4194304   8e  Linux LVM

2、创建物理卷

pvcreate /dev/sdb1 /dev/db2 /dev/sdb3 /dev/sdc1 /dev/sdc2 /dev/sdc3
pvs
pvdisplay

3、创建卷组

vgcreate myvg1 /dev/sdb1 /dev/sdb2 /dev/sdc3
  Physical volume "/dev/sdb2" successfully created.
  Volume group "myvg1" successfully created
vgcreate myvg2 /dev/sdc1 /dev/sdc2 /dev/sdb3
  Volume group "myvg2" successfully created
vgs
vgdisplay

4、激活卷组

vgchange -a y myvg1
vgchange -a y myvg2

vgchange -a n myvg1(停用)
vgchange -a n myvg1(停用)

5、创建逻辑卷

lvcreate -L 4G -n mylv1 myvg1
lvcreate -l 1533 -n mylv12 myvg1
lvcreate -l 4861 -n mylv2 myvg2
lvs
lvdisplay

6、格式化逻辑卷，创建文件系统

mkfs.xfs /dev/myvg1/mylv1
mkfs.xfs /dev/myvg1/mylv12
mkfs.xfs /dev/myvg2/mylv2

7、建立挂载目录，挂载卷

mkdir /mylv1
mkdir /mylv12
mkdir /mylv2
mount /dev/myvg1/mylv1 /mylv1
mount /dev/myvg1/mylv12 /mylv12
mount /dev/myvg2/mylv2 /mylv2
df -h | grep mylv
/dev/mapper/myvg1-mylv1 4.0G 33M 4.0G 1% /mylv1
/dev/mapper/myvg1-mylv12 6.0G 33M 6.0G 1% /mylv12
/dev/mapper/myvg2-mylv2 19G 33M 19G 1% /mylv2

 8、添加新的物理卷到卷组

fdisk -l /dev/sdd

Disk /dev/sdd: 26.8 GB, 26843545600 bytes, 52428800 sectors
Units = sectors of 1 * 512 = 512 bytes
Sector size (logical/physical): 512 bytes / 512 bytes
I/O size (minimum/optimal): 512 bytes / 512 bytes
Disk label type: dos
Disk identifier: 0xadcef81f

   Device Boot      Start         End      Blocks   Id  System
/dev/sdd1            2048     4196351     2097152   8e  Linux LVM

pvcreate /dev/sdd1
vgextend myvg2 /dev/sdd1
vgdisplay myvg2 | grep Free
  Free  PE / Size       511 / <2.00 GiB

9、修改逻辑卷大小

增加逻辑卷空间
1、利用lvextend扩展逻辑卷大小
lvextend -L +2G /dev/myvg1/mylv12
2、利用resize2fs文件系统大小
resize2fs /dev/myvg1/mylv12 32G

减小逻辑卷空间
1、卸载已经挂载的逻辑卷分区
umount /dev/myvg1/mylv12
2、利用resize2fs修改文件系统大小
resize2fs /dev/myvg1/mylv12 20G
3、利用lvreduce修改逻辑卷大小
lvreduce -L -12G /dev/myvg1/mylv12
4、挂载修改后的逻辑卷分区
mount /dev/myvg1/mylv12 /mylv12

10、删除逻辑卷，物理卷，卷组

umount /dev/myvg1/mylv1
lvremove /dev/myvg1/mylv1
umount /dev/myvg1/mylv12
lvremove /dev/myvg1/mylv12

vgreduce myvg1 /dev/sdb1
vgreduce myvg1 /dev/sdb2

pvremove /dev/sdb1
pvremove /dev/sdb2

vgremove myvg1
pvremove /dev/sdc3